Hives: A raised, itchy area of skin that is usually a sign of an allergic reaction. It can be rounded or flat-topped but is always elevated above the surrounding skin. It reflects circumscribed dermal edema (local swelling of the skin). The hives are usually well circumscribed but may be coalescent and will blanch with pressure. They typically last less than 4 hours but they may stay for days or weeks. Approximately 20% of the population has experienced a bout of hives.
The hives are also called urticaria.